BUG: fix mixed datetime regression (#2479)

CHANGELOG.md

@@ -14,6 +14,8 @@ Deprecations and compatibility notes:
     `schema_version` if `version` is one of 0.1.0 or 0.4.0 (#2496).
 
 Bug fixes:
+- Fix a crash in datetime column reading where the file contains mixed timezone
+  offsets (#2479). These will be read as UTC localized values.
 
 - Fix regression (RecursionError) in reshape methods such as ``unstack()``
   and ``pivot()`` involving MultiIndex, or GeoDataFrame construction with

geopandas/io/file.py

@@ -341,9 +341,15 @@ def _read_file_fiona(
                     f_filt, crs=crs, columns=columns + ["geometry"]
                 )
             for k in datetime_fields:
-                # fiona only supports up to ms precision, any microseconds are
-                # floating point rounding error
-                df[k] = pd.to_datetime(df[k]).dt.round(freq="ms")
+                as_dt = pd.to_datetime(df[k])
+                # if to_datetime failed, try again for mixed timezone offsets
+                if as_dt.dtype == "object":
+                    # This can fail if there are invalid datetimes
+                    as_dt = pd.to_datetime(df[k], utc=True)
+                # if to_datetime succeeded, round datetimes as
+                # fiona only supports up to ms precision
+                if not (as_dt.dtype == "object"):
+                    df[k] = as_dt.dt.round(freq="ms")
             return df
 
 

geopandas/io/tests/test_file.py

@@ -10,6 +10,7 @@ import numpy as np
 import pandas as pd
 
 import pytz
+from pandas.api.types import is_datetime64_any_dtype
 from pandas.testing import assert_series_equal
 from shapely.geometry import Point, Polygon, box
 
@@ -231,6 +232,28 @@ def test_to_file_datetime(tmpdir, driver, ext, time, engine):
         assert_series_equal(df["b"], df_read["b"])
 
 
+def test_read_file_mixed_datetimes(tmpdir):
+    tempfilename = os.path.join(str(tmpdir), "test_mixed_datetime.geojson")
+    df = GeoDataFrame(
+        {
+            "date": [
+                "2014-08-26 10:01:23.040001+02:00",
+                "2019-03-07 17:31:43.118999+01:00",
+            ],
+            "geometry": [Point(1, 1), Point(1, 1)],
+        }
+    )
+    df.to_file(tempfilename)
+    res = read_file(tempfilename)  # check mixed tz don't crash GH2478
+    assert is_datetime64_any_dtype(res["date"])
+    if FIONA_GE_1814:
+        # Convert mixed timezones to UTC equivalent
+        assert res["date"].dt.tz == pytz.utc
+    else:
+        # old fiona and pyogrio ignore timezones and read as datetimes successfully
+        assert is_datetime64_any_dtype(res["date"])
+
+
 @pytest.mark.parametrize("driver,ext", driver_ext_pairs)
 def test_to_file_with_point_z(tmpdir, ext, driver, engine):
     """Test that 3D geometries are retained in writes (GH #612)."""